The major goals of this study have been (1) to adapt newly developed methods of embryo culture for teratogenicity studies; (2) to determine the teratogenic potential of several selected drugs; and (3) to evaluate the utility of the embryo culture system for basic studies in developmental biology. These goals have been reached. Mouse embryos in culture have been used to demonstrate dose-dependent teratogenic effects of the anticonvulsants valproic acid and diphenylhydantoin in the absence of maternal modification. The suitability of embryo culture for examining the mechanism(s) by which drugs elicit teratogenic effects, as well as for applying newly developed methods of computer-assisted analysis of polyacrylamide gels after 2-dimensional electrophoresis to the proteins of a single embryo.